1. Field of the Invention
This invention relates to a machine for sorting goods that are classifiable according to size, such as fruits, and in particular to the high speed size sorting of such goods.
2. Description of the Prior Art
Photoelectric sorting machines have generally been designed to include a plurality of sorting heads, each head being provided with at least one horizontal and one vertical photoelectric sensor. Each sorting head operates on a different threshold level so as to detect articles of various sizes. Because of this, each sorting head requires its own associated circuitry, and a multiplicity of sorting heads and circuits is a major cost factor.
Another technique for machine sorting is disclosed in U.S. Pat. No. 3,142,383, issued July 28, 1964, entitled "Machine for Sorting", by J. J. Boyer, which concerns a sorting machine wherein the light beam is constituted of parallel rays. A light source is positioned at the focal point of a parabolic mirror (reflector) and a shield is employed so that only reflected light is transmitted across the path of the object to be sorted. A diaphragm is set at an aperture to permit passage of a beam whose cross-section is slightly greater than the orthogonal projection of the larger object to be sorted. The beam received on the other side of the path is concentrated by an identical parobolic mirror. Also, a shield and diaphragm are employed as were used on the transmitting side of the object path. A photoelectric cell is employed to convert the light rays into electrical current. The current produced by the cell is used to control electromagnetic valves which eject the selected article onto an alternate pathway. It is apparent from the forgoing that a plurality of such stations must be positioned along the object path, and each separate light station set to select a particular size object for sorting purposes.
In another technique used for machine sorting, as disclosed in U.S. Pat. No. 4,120,403, issued Oct. 17, 1978, "Photoelectric Apparatus for Sorting Variegated Articles According to Size", by Stephen P. Stephanos, only one station is used to make a measurement. In this case a plurality of photocells are situated on one side of an object conveyer and on the opposite side is placed a column light source. The passage of an object through the light path from the light source will interrupt a number of photocells. The number of photocells interrupted is a measure of the object size.